Study on the influence of SARA fraction in heavy oil on the oil recovery during water flooding by experiments and the molecular dynamics simulation

W/O emulsification in the J-7 reservoir has been regarded as the main reason for enhancing oil recovery. Therefore, in this article, the chemical structures of SARA fractions of JD-1 crude oil were obtained through characterization experiments, and the effect of the influence of SARA fractions on the W/O emulsification and the oil recovery by using emulsification experiments, interfacial experiments, emulsification experiments, and water flooding experiments. Results showed from emulsification experiments that the emulsification degree of the simulated oil containing asphaltenes was higher than other simulated oils. All emulsions of SARA fractions after emulsifying were W/O emulsions, but compared with other components, the performance of emulsions of asphaltenes was the best. The viscosity of emulsions reached 8.16–18.38 times that of simulated oil, the average size of was only 0.68 μm, and the stability was also very good. From interface tension and expansion modulus experiments, it can be seen that after adding asphaltenes, the decrease degree of interface tension and the increased degree of expansion modulus were the most. The result of molecules dynamic simulations showed that the adsorption force on the oil-water interface of asphaltenes was greater than other components. The water flooding experiments found the recovery of the simulated oil containing asphaltenes reached 43.81%, which was higher than other simulated oil, indicating that the easier W/O emulsification was formed, the recovery rate was higher.</p

Oxidation Behavior and Kinetics of Eight C₂₀–C₅₄ <i>n</i>‑Alkanes by High Pressure Differential Scanning Calorimetry (HP-DSC)

In this study, the oxidation behavior and kinetics of linear alkanes (C₂₀H₄₂, C₂₄H₅₀, C₃₀H₆₂, C₃₂H₆₆, C₃₆H₇₄, C₃₈H₇₈, C₅₀H₁₀₂, and C₅₄H₁₁₀) were investigated by high pressure differential scanning calorimetry (HP-DSC). It turned out that only the exothermic peak of low-temperature oxidation (LTO) was observed during the oxidation process of these linear alkanes, which is different from the oxidation behavior of the crude oil. For the crude oil, two exothermic peaks were observed: LTO and high-temperature oxidation (HTO). This means that the linear alkanes barely contributed in the HTO reaction of crude oils. In addition, the exothermic peaks in the oxidation process of all these linear alkanes overlapped each other. They showed almost the same oxidation behavior in terms of the temperature range of reaction as well as the onset and peak temperatures. It seems that the oxidation behavior of the tested linear alkanes was independent of their carbon number. It was also found that increasing pressure resulted in an increase of the heat release. The kinetics parameters of the oxidation reaction were estimated using three “model-free methods” known as Friedman, Ozawa–Flynn–Wall (OFW), and ASTM E698. The results showed that the activation energy of the LTO process of each linear alkane can be regarded as a constant average value in the range of conversion degree from 0.2 to 0.8, and all the tested linear alkanes had similar activation energy values of 80–120 kJ/mol calculated by the Friedman method and 90–110 kJ/mol calculated by the OFW method. The OFW method showed a lower error than the Friedman method when being applied to the DSC data. The values of activation energy estimated using the ASTM E698 method were 100.41, 95.61, 93.62, 100.55, and 92.47 90–110 kJ/mol for C₂₀H₄₂, C₂₄H₅₀, C₃₀H₆₂, C₃₈H₇₈, and C₅₄H₁₁₀, respectively, which are also in the same range of the values of the activation energy obtained by the Friedman and OFW methods. Similar activation energy values of different linear alkanes partly explained why they showed almost the same oxidation behavior